For several years, the Canadian Forces have been using the 20-mm M55A2 TP projectile for training pilots in attacking ground targets. The practice projectile consists of a main steel body having a copper driving band and an aluminum nose cap. Air operations, flight safety and technical staff of Air Command are becoming increasingly concerned with the ricochet hazards to aircraft during training gunnery missions, particularly when tactical target areas are used and also during the winter months when air weapon ranges cannot be sanitized of spent projectiles. Many Canadian Forces aircrafts have been damaged by projectile ricochet strikes resulting in a significant financial loss, not to mention the loss of operational aircraft during the period of repair, and the potential of destroying the aircraft and killing its air crew.
There is a need, therefore, for target practice projectile for air to ground use which will appreciably reduce, if not completely eliminate, the ricochet hazards to the aircraft during air to ground training gunnery missions. There are at least two ways of eliminating ricochet hazards. The first method is to have the projectile penetrate the target (in the present case, the ground) in which all of the energy of the projectile is dissipated during penetration. The second method is to have the projectile break-up on impact into relatively small fragments so that the non-aerodynamic shape of the fragments reduce the ricochet envelope and thus minimize the hazard to the aircraft.
Penetration of the projectile into the target is not always possible to achieve because of the high degree of obliquity used during air to ground gunnery missions where the dive angle can be as low as 5.degree.. Also, the conditions of the ground impact area are not necessarily the same for different ranges and are greatly affected by the local meteorological conditions: the soil can be wet or dry, relatively hard or soft, frozen or it can be contaminated with pieces of rocks or spent projectiles. Because of all of these variables, it is virtually impossible to design a practice projectile that will always penetrate the target during air to ground training gunnery missions.